Whole-Body Diffusion-Weighted MRI With Apparent Diffusion Coefficient Mapping for Early Response Monitoring in Multiple Myeloma: Preliminary Results

OBJECTIVE. The purpose of our study was to prospectively assess the feasibility of whole-body diffusion-weighted imaging (DWI) for short-term evaluation of response to treatment in multiple myeloma patients using a single-shot echo-planar imaging DWI sequence with a Stejskal-Tanner diffusion encoding scheme and spectral fat suppression. SUBJECTS AND METHODS. Twelve consecutive patients (nine men and three women; mean age, 61.4 years; age range, 54-79 years) underwent whole-body DWI (b = 50, 400, and 800 s/mm(2)) both at baseline and 3 weeks (mean, 23 days) after onset of therapy. Bone marrow and extramedullary manifestations were evaluated by quantitative image analysis using measurements of the mean apparent diffusion coefficient (ADC). These parameters were correlated with myeloma response according to standard criteria and were evaluated parallel to MRI and continuously for more than 6 months afterward. RESULTS. Fifty-three myeloma lesions, 50 medullary (28 axial and 22 appendicular skeleton) and three extramedullary, were analyzed. Eleven patients were classified as responders and one as a nonresponder. DWI results accurately (100%) correlated with disease course according to standard clinical and laboratory criteria. All involved lesions showed restricted diffusion at baseline. ADC quantification yielded an increase of 63.9% (range, 8.7-211.3%) in responders and a decrease of 7.8% in the sole nonresponding patient during therapy. In parallel, M-gradient measurement showed a mean decrease of 45.1% (range, 19.6-88.8%) in responders and an increase of 21.8% in the nonresponder. Amplitude of response measured by the course of ADC values proved higher in the appendicular skeleton (99.8%) compared with the axial skeleton (54.3%) (p = 0.037). CONCLUSION. Whole-body DWI with ADC analysis represents a feasible diagnostic tool for assessment of short-term treatment response in myeloma patients.